US2002/0064702 discloses a fuel cell in which the number of grooves distributing fuel gas in an anode side separator is differentiated from the number of grooves distributing oxygen gas in a cathode side separator, to thereby differentiate cross sections (specifically, total cross section of grooves) of reaction gas passages disposed in the respective electrode side separators. Alternatively, for the same number of grooves between the two electrode side separators, cross section of one groove is differentiated.